1. Field of the Invention
The present invention relates to a display apparatus having a fluorescent member for displaying an image and the like and support rods disposed in a displaying envelope for accommodating an electron source for exciting the fluorescent member at a predetermined distance between an anode substrate and a cathode substrate disposed opposite to each other, and more particularly to a display apparatus having a field emission cathode.
2. Description of the Related Art
When an electric field of about 10.sup.9 V/m is applied to the surface of a metal or semiconductor member, a tunnel effect causes electrons to pass through a barrier so that electrons are discharged into a vacuum although it is under the normal temperature. The foregoing phenomenon is called "field emission" and is a known phenomenon. A cathode for discharging electrons by using the above-mentioned principle is called a field emission cathode.
In recent years, the use of techniques for micro-machining semiconductors enables the manufacture of a micro-sized field emission cathode. By forming a multiplicity of the field emission cathodes on a substrate, a surface emission type field emission array can be manufactured. A field emission array of the above-mentioned type has been suggested to be employed as an electron source of a display apparatus, a CRT, an electronic microscope, an electron beam apparatus and the like.
The cross sectional structure of a conventional display apparatus is shown in FIG. 1 as an example of an employment of the above-mentioned field emission array. The display apparatus shown in FIG. 1 has a structure such that a glass cathode substrate 10 having a field emission array and an anode substrate 4 having a fluorescent member and made of transparent glass are disposed opposite to each other so that an envelope capable of evacuating the inside thereof is formed.
The field emission array formed on the cathode substrate 10 is a spindt type field emission array including stripe-shaped cathode line electrodes 6 formed by sputtering or the like, a resistance layer 9 formed on the cathode line electrodes 6, an emitter cone group 7 formed on the resistance layer 9 and gate line electrodes 5 formed adjacent to the leading ends of the emitter cone group 7.
Note that an insulating layer 8 is laminated on the resistance layer 9, and the gate line electrodes 5 are formed on the insulating layer 8.
The pitch between the emitter cones of the emitter cone group 7 can be shortened to 10 microns or more. The emitter cones are formed on one cathode substrate 10 by tens to hundreds of thousands. Since the field emission array of the foregoing type enables the distance between the gate and the cathode to be shortened to a sub-micron value, electrons can be emitted from the emitter cone group 7 by applying voltage V of only tens of volts between the gate and the cathode.
The anode substrate 4 has the anode electrode 1 formed thereon, and a fluorescent dot pattern 2 is laminated on the anode electrode 1.
Therefore, when a positive voltage V is applied to the anode electrode 1, electrons emitted from the emitter cone group 7 are caught by the anode electrode 1. Electrons caught as described above conflict with the fluorescent dot pattern 2 laminated on the anode electrode 1 so that the fluorescent dot pattern 2 is excited. As a result, the fluorescent dot pattern 2 emits light. Light emission at this time can be observed through the anode substrate 4.
In the display apparatus having the above-mentioned structure, the inside of the envelope formed by the cathode substrate 10 and the anode substrate 4 is made to be under high vacuum. Since the cathode substrate 10 and the anode substrate 4 are sometimes impossible to maintain at a predetermined distance because of an influence of the atmosphere, a plurality of insulating support rods 3 are disposed between the cathode substrate 10 and the anode substrate 4.
Each insulating support rod 3 is made of an insulating material, for example, glass, the plurality of the insulating support rods 3 being disposed between the cathode substrate 10 and the anode substrate 4 at predetermined intervals.
The top end of the insulating support rod 3 is arranged to be in contact with the anode electrode 1 formed on the anode substrate 4, while the bottom end of the insulating support rod 3 is disposed in contact with a gate line electrodes 5 formed on the insulating layer 8 of the cathode substrate 10.
The plurality of stripe-shaped cathode line electrodes 6 formed on the cathode substrate 10 and the stripe-shaped gate line electrodes 5 formed perpendicularly to the cathode line electrodes 6 form a matrix. The matrix is scanned by a cathode scanning portion (not shown) and a gate scanning portion (not shown).
As a result, electrons are selectively emitted from the emitter cone group 7 in response to the image signal so that the fluorescent dot pattern 2 emits light. Thus, an image is displayed on the anode substrate 4.
In this case, for example, an image signal is supplied to the gate scanning portion so that one image is displayed on the anode substrate 4 when scanning of one field is completed.
It is preferable that the display apparatus having the above-mentioned structure has improved characteristics by minimizing factors which deteriorate the light emission efficiency of the fluorescent dot pattern 2 and emission performance of the emitter cone group 7, which shorten the life of the display apparatus.